In recent years, robot-assisted procedures for surgery and therapy have received considerable attention and are often preferred over conventional, manually performed procedures because of a robot's ability to perform consistent precise movements free of fatigue and tremor, and carry out surgical procedures with high dexterity and accuracy beyond those of a surgeon.
However, many surgical applications require the ability to accurately and conveniently manipulate and re-orient a special purpose surgical tool, e.g. manipulation of laparoscopic cameras and external beam radiation, biopsy sampling, precise tissue removal, precise radioactive seed implantation for prostate and lung brachytherapies, localized drug delivery using needles, catheter insertion and the like. These applications require accurately controlled motion, e.g. re-orientation of a tool, under computer control, while strictly limiting undesired motions. Moreover, many of these applications require relatively slow computer-controlled precise motions. While it is difficult for a human surgeon to perform such motions, it can be easily accomplished consistently by utilizing a special purpose robotic mechanism to perform it.
It is worth noting that such procedures need the ability to manipulate and re-orient the tool (needle, surgical tool, saw. etc.) about a pivot point, also called Remote Center-of-Motion (RCM), typically it is the point of entry of a surgical tool into the patient's internal organs. In a conventional robot (e.g. industrial robots), motions about an RCM are achieved by coordinated motions of multiple joints, many of which may be required to move rapidly through a large workspace in order to achieve relatively small tool reorientations. Thus, relatively fast joint motions may be needed to cause quite rapid end effector re-orientation. This increases the potential to injuries and may cause collisions, i.e. robot-patient or robot-equipment collisions. Also when small joint actuators are used or joint velocities are limited for safety considerations, many desired tool motions may become extremely slow.
Also, because of the limited and constrained workspace of surgical environments, surgical mechanisms need to be designed with special configuration that allows for miniaturization and to have compact sizes in order to interact easily with the patient and other existing equipment. Again this enhances the robot's maneuverability but presents another challenge to the design and implementation of the mechanism kinematics, given the working volume restrictions.
Some robotic systems for needle insertion or tool re-orientation have been reported in the literature. The most notable being a system for the augmentation of surgery with a remote center-of-motion manipulator reported in [R. Taylor, J. Fonda, D. Grossman, J. Karidis and D. LaRose, “Remote Ceter-of-Motion Robot for Surgery”, U.S. Pat. No. 5,397,323, 1995.]. It adopts a double parallelogram structure. However, its working radius forms a main trade off. If a large working radius for the tool is desired, the resulting robot structure can become somewhat clumsy and obstructive in the operating room and can impede access to the patient. Also, if the working radius is small, then the mechanism may get in the way of the surgeon's hands, instruments or direct vision.
A related consideration is that high quality mechanism can be expensive and difficult to fabricate. Another mechanism presented in [H. Bassan, R. V. Patel and M. Moallem, “A novel manipulator for prostate brachytherapy: Design and preliminary results”, Proc. of the 4th IFAC Symposium on Mechatronics Systems, 2006, pp. 30-35.] was designed to perform an RCM. Since the main structure was based on the mechanism introduced by R. Taylor et. al., it demonstrated the same drawbacks mentioned above. Also, the PAKY/RCM was developed at Johns Hopkins University and reported in several publications [G. Fichtinger, T. L. DeWeese, A. Patriciu, A. Tanacs, D. Mazilu, J. A. Anderson, K. Masamune, R. H. Taylor, and D. Stoianovici, “System for robotically assisted prostate biopsy and therapy with intraoperative CT guidance”, Journal of Academic Radiology, volume 9, 2002], [D. Stoianovici, K. Cleary, A. Patriciu, D. Mazilu, A. Stanimir, N. Craciunoiu, V. Watson, and L. Kavoussi, “Acubot: A robot for radiological interventions”, IEEE Trans. on Robotics and Automation, volume 19, 2003]. The robot consists of three independent stages for needle positioning, orientation and insertion.
Another mechanism for needle insertion/reorientation is described in [K. Chinzei and K. Miller, “Towards MRI guided surgical manipulator”, Int. Medical Journal for Experimental and Clinical Research, volume 7, 2001]. The design utilizes planar drives similar to that of Kronreif [G. Kronreif, M. Fürst, J. Kettenbach, M. Figl, and R. Hanel. Robotic guidance for percutaneous interventions. In Journal of Advanced Robotics, volume 17, 2003] to create an RCM. Again, the sizes of these manipulators are quite large and they are unsuitable for use in surgical applications.